How Jet Lag Works

Resetting the body's natural clockwork is a lot tougher than remembering which buttons to press down on your Timex Ironman. The average free-running period of the human circadian clock actually is slightly longer than 24 hours, so most of us have a natural tendency to drift slightly later each day. That may be why the body adjusts better to phase delay (flying east to west) mode than it does to phase advance (west to east) mode, which necessitates going to bed earlier. In one study, it took subjects four days to adjust to a 12-hour phase delay, while a comparison group undergoing a 12-hour phase advance still couldn't get to sleep normally eight days later [source: Eastman and Burgess].

Another complication is that light isn't the only thing that influences sleep. Your body's temperature also fluctuates during sleep, reaching its minimum temperature ("Tmin," in sleep-scientist lingo) about three hours before you normally rise. Jet lag symptoms tend to be the worst when you are forced to awaken while you are still at your normal Tmin. That's why you may feel out of sorts and mentally dull, even after what seems like a full night's sleep [source: Eastman and Burgess].

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Over the years, travelers have experimented with numerous remedies for jet lag. Some people just try to gut it out, even though staying up all night and all through the next day until bedtime isn't exactly a good thing for your body or your mental health. Others swear by herbal remedies, or by taking additional melatonin, which is sold as a supplement. Still others try to circumvent jet lag by taking overnight flights and trying to snooze in their seats, with the help of a sleeping medication. Doctors, however, advise strongly against this last solution. The human body, as it turns out, is not designed for deep sleep while sitting, and immobilizing a person for long periods in that position escalates the risk of thrombosis, the formation of blood clots. The New England Journal of Medicine recently documented the case of an otherwise healthy 36-year-old woman who, after sleeping in an airliner seat for seven hours, suffered what turned out to be a fatal stroke [source: Schneider].

But don't fret. In the next section, we'll give you some advice from medical and travel experts on safer, more effective ways to cope with jet lag.